A very tiny fly

This little guy was on my yucca flower stalk. The flower stalk is covered with tiny little yellow bugs(larvae?) that metamorphose into these tiny flies. The flower stalk gets chewed on by the tiny larva, and then exudes sticky sap, which in turn leads to more bugs. From watching this happen on yuccas at the university, eventually ants seem to be attracted, and they set up a bug farming operation, and crawl over the larvae and plant collecting sap balls. I secretly am hoping for ants, but given that my granddaughter is afraid of them and that her grandfather who takes care of her at my house a couple of afternoons a week really hates them, I believe that there is no chance of a colony get established.

I give thanks for the wonders of nature, including yuccas, tiny flies and ants.

Update: The yellow bugs are aphids and don't metamorphose into the flies, which are midges. The little ecosystem is more complex than the aphids and the midges which eat the aphids. There appear to be other predators.